Continued effort will be made to generate and characterize monoclonal antibodies specific for later stages of B-cell differentiation. Special emphasis will be made in the identification of plasma cell-\and myeloma cell-specific antigens. Human T-T hybridoma technology will continue to be developed and the feasibility of fusion under micromanipulation will be tested. T-cell factors generated by T-T hybridoma and specific for IgM and IgG secretion, as well as factors for Ig isotype switching, will be identified. Emphasis also will be made to identify hidden serum Ig band in CLL patients and to ascertain the feasibility to generate anti-idiotypic monoclonal antibodies to the hidden serum Ig band. T-cell factors which would induce CLL cells to proliferate will be sought. These studies will yield information significant for our understanding of normal and neoplastic B-cell proliferation and differentiation.